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Full text of ""184" cyclotron synchroscope beam pictures on two probes"

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MDDC - 987 








Fred W. Yeater, Jr. 

University of California 

Published for use within the Atomic Energy Commission. Inquiries for additional copies 
and any questions regarding reproduction by recipients of this document may be referred 
to the Documents Distribution Subsection, Publication Section, Technical Information 
Branch, Atomic Energy Commission, P. O, Box E, Oak Ridge, Tennessee. 

Inasmuch as a declassified document may differ materially from the original classified 
document by reason of deletions necessary to accomplish declassification, this copy does 
not constitute authority for declassification of classified copies of a similar document 
which may bear the same title and authors. 

Date of Manuscript: February 26, 1947 
Document Declassified: May 26, 1947 
This document consists of 4 pages. 

Digitized by tine Internet Archive 

in 2011 witln funding from 

University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation 


- 1 - MDDC - 987 


By Fred W. Yeater, Jr. 

Experiment done by Fred W. Yeater, Jr., Ralph Dufour, Albert Oliver 


The described experiment was performed in an effort to determine more definitely 
that the peaks, or "pips," shown in synchroscope photographs of the beam current are 
caused by precession of the beam. 


An auxiliary copper probe, shielded for RF pickup, was introduced into the main 
vacuum tank through a Wilson seal on the port near the ion source in such a manner as to 
generate a 155° angle with the regular probe. (See Figure 1.) This auxiliary probe was 
made adjustable as to its radial depth, and equipped to supply a beam signal to the s3mchro- 
scope in addition to that signal supplied by the regular probe. 

Several photographs were taken in the usual manner under the following conditions: 

Magnet current 1500 amp 

Dee voltage (RF) 16 kv 

Capacitor speed 240 rpm 

Pulse length 5 microsec. 


The usual beam pattern of two to three pips was obtained at several probe radii; 
namely, 22 , 28 1/2 and 35 , Then, when the auxiliary probe was positioned to catch 
some of the accelerated ions, the beam pattern was altered to show the relative ampli- 
tudes of beam current in the two probes and the phase relation of those currents. 

This effect is shown most clearly in those photographs numbered 11 to 14, inclusive. 
(There were five additional photographs to complete this series which imfortunately do 
not exist due to camera trouble.) 

Following is a brief description of the photographs. Operating values are as Listed 
previously and the regular probe radius was 28 1/2 ' . 

MDDC 987 

- 8 - MDDC - 987 

Photograph No. 11: Auxiliary probe radius 28' 1/4 
Beam current .55 x 10''' amp 

This photograph shows the beam to be occurring 180 microseconds 
after the arc pulse (10 microsecond markers). 

Photograph No. 12: Same conditions as above, but with expanded synchroscope sweep 
showing the beam to be 25 microseconds In width. 

Photograph No. 13: Auxiliary probe radius 27 13/16" 
Beam current .35 x 10"'^ amp 

The pips produced by the auxiliary probe are readily apparent, 
as is the drop in beam current amplitude. 

Photograph No. 14: Auxiliary probe radius 27 9/16 
Beam current ,25 x 10"'^ amp 

Beam current is more equally divided between the two probes, and 
the phase relationship between these currents is more apparent. 

Note: In all the above photographs, the beginning of the synchroscope sweep was 

triggered at a point on the RF cycle corresponding to a frequency of 11.06 mc. 

The remainder of this series would have shown the pips produced by the regular 
probe to drop in amplitude while those produced by the auxiliary probe increased propor- 
tionately as the radius of the auxiliary probe was decreased, until such time as the 
auxiliary probe was catching essentially all the ions. At this time the pattern was a 
series of triangular vanes of equal amplitude. This pattern actually changed very little, 
if any, from that point where the current distribution was equal to the point where all the 
current was on the auxiliary probe. The logical end result would have been a pattern 
similar to the original, shown in Photograph No. 12, with a 1550 phase shift. 

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MDDC - 987 

Photograph No. 11 



Photograph No. 12 



Photograph No. 13 

Photograph No. 14 


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